Even though the Web Bluetooth API specification is not finalized yet, we can
already play with it as it's partially implemented in Chrome OS M45
behind an experimental flag. Go to chrome://flags/#enable-web-bluetooth, enable
the highlighted flag, restart Chrome and you should be able to scan for and
connect to nearby Bluetooth devices and read/write Bluetooth characteristics.

Demo

Scan for Bluetooth Devices

It is worth mentioning again there that due to security
requirements,
Web Bluetooth will only work for HTTPS websites. We would recommend you set up
HSTS for enforcing HTTPS on your website. If
you don't control the server, check out our new
<platinum-https-redirect>
element.

One of our favorite ways to write though is to use the auto-write property of
the <platinum-bluetooth-characteristic> element. When set to true, changes
in value will automatically drive characteristic writes.

As always, if you have any questions around how this works, please feel free to
use the polymer tag on
StackOverflow, or join us on the Polymer Slack
Channel.